This invention relates to the drawing of refractory metal wire and more particularly to a method of heating the wire during the wire drawing process.
Various methods have been employed over the years for heating wire during the wire drawing process. Some of the earliest efforts in heating wire for purposes of drawing the wire were disclosed by Thomas A. Edison in U.S. Pat. Nos. 436,969 and 563,462. In U.S. Pat. No. 436,969 a series of gas fires were directed at a porcelain or nickel tube which constituted a heating chamber for the wire to be drawn. In U.S. Pat. No. 563,462 the wire was heated by direct electrical contact which provided electrical resistance heating of the wire in a non-oxidizing atmosphere.
F. F. Fowle in U.S. Pat. No. 1,896,613 discloses the heating of zinc-coated wire in a preheating furnace in which the wire passes through a central chamber of a furnace which is heated by fires. McKeen et al. in U.S. Pat. No. 2,057,582 discloses a wire drawing and annealing process in which an axial burner is employed to heat the wire before it enters an adjacent cooling chamber. U.S. Pat. No. 2,187,785 to M. A. Hoyt discloses the use of an electric furnace to dry the lubricated wire in which the lubricated wire passes through a resistance tube which is electrically resistance heated to perform the heating function prior to drawing. In U.S. Pat. No. 2,325,342 there is disclosed a gas heating chamber which heats the wire after it has been reduced by the drawing die and before the wire enters a cooling chamber.
At least some manufacturers in present day refractory wire drawing processes employ a plurality of flames to dry the lubricant on the wire and to preheat the wire before it enters the wire drawing die. This system generally involves a large number of gas fires impinging directly on the wire and creates a high noise level, tremendous heat in the surrounding environment and utilizes an excessive amount of gas involving a substantial energy waste.